The Forkhead genes (transcription complex Fox) play many important roles in the maintenance and determination of biological processes underlying carbon-based life. The expression of Fox genes occurring as a result of reciprocal interactions at the transcriptional level influences the correct function of the immune system as regards the context of general activity of immunological parameters, as well as exposure to aetiological agents. In the case of model organisms and species, in which the knowledge about genomic sequences is incomplete, understanding the above-mentioned transcriptional complex is still insufficient, despite the existence of numerous scientific publications. It is worth noting that Fox genes exist in amphioxus Branchiostoma lanceolatum and in the majority of species they were not characterised. Among many coding sequences included in the transcriptional complex Forkhead, Foxp3, Foxn1, and Foxj1 genes are of a great importance from immunological point of view, being partially jointly responsible for determining features related to productivity. The paper provides general characterisation of selected Fox genes and is an introduction to the presentation of new data, which can be applied at the level of biological differentiation of the populations of domestic and wild animals.